In order to facilitate the flow of air and adjust room temperature in a most economic and effective way, the inner spaces of general buildings are usually fitted with oscillating fans, which are either suspended from the ceiling or fixed on the walls.
In older suspended fans and fixed fans, the main features on their control panel are concerned with controlling the on/off status of the fans. Although the feature of speed controller has been added later on, such features are mainly concerned with the control of rotation speed of fans, and most of the control switches lack any protection against power overload. A good example can be found in U.S. Pat. No. 4,724,286.